How to Understand Energy Efficiency Ratings

By Gus Stephens

Understanding energy efficiency ratings helps you control operating costs in the home and intelligently comparison-shop when making buying decisions about a new appliance. Generally, the energy efficiency of a device relates to the amount of utilization you receive versus the amount of energy the device consumes. The Department of Energy's Energy Guide sticker affixed to many appliances provides an at-a-glance rating system for determining the relative energy efficiency of the product.

woman buys the refrigerator in shop
credit: 97/iStock/Getty Images
A woman shops for a refrigerator at a department store.

Sticker Shop

When shopping for appliances like washers and refrigerators, note the annual cost of electricity, displayed as a dollar figure on the Energy Guide sticker. The sticker also includes an arrow indicating the product's comparative ranking on a scale of competing models. If you know your local price of electricity per kilowatt-hour -- usually shown on your monthly utility bill -- you can use the average kilowatt-hour consumption figure shown on the sticker to more accurately calculate operating costs for your specific location.

Keep an Eye on EER

To evaluate the efficiency of room air conditioners -- also known as window units -- check the energy efficiency ratio on the Energy Guide sticker. This figure is derived in laboratory tests by calculating the kilowatt-hours of electricity consumed in ratio to the British thermal units of heat energy extracted from the air during one hour at a fixed outdoor temperature. The higher the EER numeral, the more energy-efficient the unit. Depending on the size, room air conditioners are required to have an EER rating of at least 8.0 and sometimes greater than 9.8.

SEER Is Cool

The seasonal energy efficiency ratio rating shown on the Energy Guide label for central air conditioners expresses the ratio between electrical consumption and Btu capacity across a range of temperatures averaged over the length of a typical cooling season. At the time of publication, the federal national minimum SEER is 13. Beginning Jan. 1, 2015, minimum SEER ratings will be determined by geographic zone. While northern states will retain the SEER 13 standard, in the South and Southwest the SEER minimum will rise to 14. High-efficiency air conditioners offer SEER ratings above 20. Savings from lower operating costs, however, must be carefully balanced against the significantly higher upfront purchase price of these units.

AFUE Means Heat

Look for the Annual Fuel Utilization Efficiency standard on the Energy Guide sticker when shopping for a gas-fired or electric furnace. AFUE expresses the percentage of energy that actually generates heat vs. energy lost in the process. Currently, the nationwide AFUE minimum is 78 percent. On Jan. 1, 2015, the minimum increases to 80 percent for gas furnaces and 83 percent for oil-fired furnaces. High-efficiency furnaces that recover some combustion losses deliver AFUE ratings above 90, but at a higher initial purchase price. Don't compare apples and oranges when evaluating AFUE ratings of electric vs. gas heating systems. Because electric furnaces have no combustion losses, AFUE ratings are typically close to 100 percent. In most regions, however, the substantially higher cost of electricity makes an electric furnace actually more expensive to operate than a standard gas-fired furnace, despite the electric unit's higher AFUE.